A method of molten metal casting utilizing an impact pad in the tundish

ABSTRACT

A method of molten metal casting utilizing an impact pad in the tundish introduces that the molten metal is transported into the tundish, at the bottom of which is located the impact pad with the spherical top, which captures the initial impact flow, the flow of molten metal is optimized and the molten metal is led away from the tundish.

TECHNICAL FIELD

The present invention relates to a method of molten metal casting utilizing an impact pad with spherical top in the tundish.

BACKGROUND ART

Tundish is usually weldment of steel plates with reinforcing ribs and is provided with a refractory lining. The tundish nozzles are walled in the bottom of the tundish. The fact is that the tundish operations can affect the quality of the molten metal just before casting, so the development of tundish metallurgy is very important.

The tundish meets various metallurgical functions as a reservoir of liquid molten metal before casting and it is the transporter of molten metal or steel for individual casting streams during changing the ladle, minimizes the casting flow splash, reduces ferrostatic pressure of the molten metal, homogenized molten metal chemically and thermally, separates the liquid metal from slag, evaluates the casting speed, monitor the temperature of the molten metal, it uniforms the speed in casting, maintains a steady constant flow of molten metal, maintains a constant liquid metal level in the crystallizer, therein the non-metallic inclusions are decanted, therein is possible to apply the most recent metallurgical operations like doping for example. In the tundish there is adjusting the retention time, also dead volume etc. by the controlling of the flow. At present, there is the major objective of the use of tundish as a tool for minimizing transitional areas and dead volumes.

Final quality of steel depends on the possibility of as little slag dragging and maximal depletion of non-metallic inclusions, and therefore it is necessary to reach the optimal flow in the tundish. The flow of molten metal thought the tundish has hydrodynamic character, which includes single-phase turbulent flow and multiphase flow, when the retention time is separated, the amount of inclusions increases according to their movement, the thermal energy is moved and the swirl is generated at the beginning and end of the casting process. For achieving an optimum casting flow and thus a higher purity of metal, it is important to secure: higher average retention time, reduction of strong turbulence and dead areas, coagulation acceleration in capable turbulent zones and flowing inclusions by active cover slag and elimination of open “red” eye produced the sprue cup on the surface of molten metal, causing the absorption of air. The residual metal and slag, which remaining in the tundish should be mechanically removed before the next casting. otherwise this slag is recycling. but its removing is laborious and it prolonging the time of continual casting. Another problem is the dead volume, leading to heat loss and conflux formation next to tundish nozzles and then their sealing. Therefore flow in the tundish must be kept by optimal control of the direction of flow and thermal gradients.

Till now there are used special tundish equipment as necessary dampers, dams, weirs, impact pads, blocks for blowing out by the inert gas.

Till now there is used the mechanical baffle “Crash tundish pad” according Slovak patent file No. 288043, which contains basic desk with upper impact surface surrounded side wall with bordered tunnels. Crash tundish pad is created in such way that let shower on itself and deflect supply flow of molten metal and allow the effluxion deviated flow through canals and open upper pad surface. The arc stepped parts surrounding the canals and/or walls like weir help to control effluxion. Separation and distribution of effluxion facilitates the development of plug flow in the molten metal between the impact pad and the tundish outlet opening. Liquid metal flow is spreading after bottom of the tundish to the tundish nozzles indeed, in the upper corners of the tundish are created dead zones.

DISCLOSURE OF INVENTION

A method of molten metal casting utilizing an impact pad in the tundish eliminates or significantly limits the disadvantages noted above. The nature of invention consists in that the molten metal is bringing into the tundish, at the bottom of which is located the impact pad with the spherical top, which captures the initial impact flow, the flow of molten metal is accelerated and optimized in terms of total volume. Tundish nozzles are opened after reaching the desired height of molten metal in the tundish, while the molten metal top is constant and the amount of flow in metal is equal to amount of metal which is leaved from the tundish through tundish nozzles to the next continuous casting equipment.

A method of molten metal casting utilizing an impact pad is proposed either for the regime of molten metal casting with changed characteristics, hence when there is molten metal with another quality in next ladle as it was in the previous ladle and therefore the tundish must be the most empty as possible, because the steel created by the mixture of the first and next ladle is unsaleable. The casting speed varies when the ladle is changing etc. and therefore the innovative casting method extends the retention time at lower and higher casting speeds. The molten metal is bringing into the tundish at the bottom of which is located the impact pad with the spherical top, which captures the initial casting flow, eliminates the impact energies, the liquid metal is led away from the tundish in the total potential tundish volume through the upper tundish nozzles and submerged entry nozzles to the next continuous casting equipment.

The advantage of said method of molten metal casting utilizing an impact pad is that there is eliminated the short circuit flow also at low casting speed, in the tundish there is avoiding the formation of dead zones, red eye effect on the surface of molten metal, the drag of tundish slag to the metal volume is not coming, in the practice there is signified by positive impact of the metal purity from a point of view of inclusions. An economic loss arising out of failure to sell steel of undetermined quality, arising from not emptied tundish is eliminated by the said method of casting.

BEST MODES FOR CARRYING OUT THE INVENTION

The molten metal is pouring into the tundish, at the bottom of which is located the impact pad with the spherical top, which captures the initial impact flow, prevents the molten metal splash, the flow of molten metal is accelerated and optimized in terms of total volume and eliminated the impact energies. Tundish nozzles are opened after reaching the desired height of molten metal in the tundish, while the molten metal top is constant and the amount of flow in metal is equal to amount of metal which is leaved from the tundish through tundish nozzles to the next continuous casting equipment.

A method of molten metal casting utilizing an impact pad is proposed either for the regime of molten metal casting with changed characteristics, hence when there is molten metal with another quality in next ladle as it was in the previous ladle and therefore the tundish must be the most empty as possible, because the steel created by the mixture of the first and next ladle is unsaleable. The casting speed varies when the ladle is changing etc. and therefore the innovative casting method extends the retention time at lower and higher casting speeds. The molten metal is bringing into the tundish at the bottom of which is located the impact pad with the spherical top, which captures the initial casting flow, eliminates the impact energies, the liquid metal is led away from the tundish in the total potential tundish volume through the upper tundish nozzles and submerged entry nozzles to the next continuous casting equipment.

INDUSTRIAL APPLICABILITY

The invention is industrial applicable in the field of metallurgy, particularly for the production of steel alloys, allowing big steel mills to meet the requirements of small amounts of alloy steel and economically efficient use of existing facilities,

CITATION LIST

Patent Literature: SK 288043 

1. A method of molten metal casting utilizing an impact pad in the tundish, characterized in that molten metal is transported into the tundish, at the bottom of which is located the impact pad with the spherical top, which captures the initial impact flow, the flow of molten metal is accelerated and optimized in terms of total volume, also the residence time is extends at lower even at higher casting speeds and tundish nozzles are opened after reaching the desired height of molten metal in the tundish, while the molten metal top is constant and the amount of flow in metal is equal to amount of metal which is leaved from the tundish through tundish nozzles to the next continuous casting equipment.
 2. A method of molten metal casting utilizing an impact pad in the tundish, characterized in that molten metal is transported into the tundish, at the bottom of which is located the impact pad with the spherical top, the liquid metal flow is optimized then the liquid metal is led away from the tundish in the total potential tundish volume through the upper tundish nozzles and submerged entry nozzles to the next continuous casting equipment. 